Carbon nanotubes can be classified by the number of walls in the tube, single-wall, double wall and multiwall. Carbon nanotubes are currently manufactured as agglomerated nanotube balls, bundles or forests attached to substrates. Use of carbon nanotubes as a reinforcing agent in elastomeric, thermoplastic or thermoset polymer composites is an area in which carbon nanotubes are predicted to have significant utility. However, utilization of carbon nanotubes in these applications has been hampered due to the general inability to reliably produce individualized carbon nanotubes and the ability to disperse the individualized carbon nanotubes in a polymer matrix. Bosnyak et al., in various patent applications (e.g., US 2012-0183770 A1 and US 2011-0294013 A1), have made discrete carbon nanotubes through judicious and substantially simultaneous use of oxidation and shear forces, thereby oxidizing both the inner and outer surface of the nanotubes, typically to approximately the same oxidation level on the inner and outer surfaces, resulting in individual or discrete tubes.
The present invention differs from those earlier Bosnyak et al. applications and disclosures. The present invention describes a composition of discrete, individualized carbon nanotubes having targeted, or selective, oxidation levels and/or content on the exterior and/or interior of the tube walls. Such novel carbon nanotubes can have little to no inner tube surface oxidation, or differing amounts and/or types of oxidation between the tubes' inner and outer surfaces. These new discrete tubes are useful in many applications, including plasticizers, which can then be used as an additive in compounding and formulation of elastomeric, thermoplastic and thermoset composite for improvement of mechanical, electrical and thermal properties.
One embodiment of the present invention is a composition comprising a plurality of discrete carbon nanotubes, wherein the discrete carbon nanotubes comprise an interior and exterior surface, each surface comprising an interior surface oxidized species content and an exterior surface oxidized species content, wherein the interior surface oxidized species content differs from the exterior surface oxidized species content by at least 20%, and as high as 100%, preferably wherein the interior surface oxidized species content is less than the exterior surface oxidized species content.
The interior surface oxidized species content can be up to 3 weight percent relative to carbon nanotube weight, preferably from about 0.01 to about 3 weight percent relative to carbon nanotube weight, more preferably from about 0.01 to about 2, most preferably from about 0.01 to about 1. Especially preferred interior surface oxidized species content is from zero to about 0.01 weight percent relative to carbon nanotube weight.
The exterior surface oxidized species content can be from about 1 to about 6 weight percent relative to carbon nanotube weight, preferably from about 1 to about 4, more preferably from about 1 to about 2 weight percent relative to carbon nanotube weight. This is determined by comparing the exterior oxidized species content for a given plurality of nanotubes against the total weight of that plurality of nanotubes.
The interior and exterior surface oxidized species content totals can be from about 1 to about 9 weight percent relative to carbon nanotube weight.
Another embodiment of the invention is a composition comprising a plurality of discrete carbon nanotubes, wherein the discrete carbon nanotubes comprise an interior and exterior surface, each surface comprising an interior surface and an exterior surface oxidized species content, wherein the interior surface oxidized species content comprises from about 0.01 to less than about 1 percent relative to carbon nanotube weight and the exterior surface oxidized species content comprises more than about 1 to about 3 percent relative to carbon nanotube weight.
Another embodiment of the invention is a stable gel consisting of discrete carbon nanotubes, wherein the discrete carbon nanotubes are individually coated with water, oils, waxes, nitric acid, or sulfuric acid. This coating prevents the formation of Van der Waals, electrical, or electrostatic forces between the discrete carbon nanotubes, thereby preventing the carbon nanotubes from agglomerating. In some embodiments, the gel may comprise as much as 99% coating material and as little as 1% carbon nanotubes by weight. In other embodiments, the gel may contain as much as 2% CNTs, or as much as 3% CNTs, or as much as 5% CNTs, or as much as 7% CNTs, or as much as 10% CNTs, or as much as 15% CNTs, or as much as 25% CNTs by weight. Removing the water or other coating material from the gel by drying would lead to the formation of anhydride, Van der Waals, electrostatic, or other bonds between the carbon nanotubes. The formation of these bonds would lead to the CNTs re-agglomerating and ceasing to be discrete carbon nanotubes. Surprisingly, the use of surfactants is not typically required in the formation of the disclosed gels and thus there is little to no surfactant contained within the gel. This allows the incorporation of discrete carbon nanotubes into a matrix without the use of a surfactant which may reduce the connectivity or crosslinking of the matrix or otherwise interfere with the desired mechanical properties of the matrix.
The discrete carbon nanotubes of any composition embodiment above preferably comprise a plurality of open ended tubes, more preferably the plurality of discrete carbon nanotubes comprise a plurality of open ended tubes. The discrete carbon nanotubes of either composition embodiment above are especially preferred wherein the inner and outer surface oxidation difference is at least about 0.2 weight percent.
The compositions described herein can be used as an ion transport. Various species or classes of compounds/drugs/chemicals which demonstrate this ion transport effect can be used, including ionic, some non-ionic compounds, hydrophobic or hydrophilic compounds.
The new carbon nanotubes disclosed herein are also useful in ground water remediation.
The compositions comprising the novel discrete targeted oxidized carbon nanotubes and also be used as a component in, or as, a sensor.
The compositions disclosed herein can also be used as a component in, or as, drug delivery or controlled release formulations.
The compositions disclosed herein may be used as a structural scaffolding for catalysts. As discussed, catalysts, enzymes, proteins, peptides or other small or large molecules may be attached to the exterior of the disclosed carbon nanotubes. The disclosed nanotube scaffolding may be useful for positioning the attached catalysts within a matrix, positioning multiple catalytic proteins or molecules with respect to each other.
Carbon nanotube scaffolding may be created by attaching a ligand or connecting molecule to the exterior surface of a group of discrete carbon nanotubes and attaching a complimentary receptor or binding molecule to the exterior surface of a second group of discrete carbon nanotubes. If these two groups of nanotubes are dispersed, the connecting and complimentary binding molecules will be allowed to bind to each other, thereby indirectly connecting the nanotubes to which the connecting and bind molecules were attached Examples of such complimentary molecules include complimentary strands of DNA or RNA, proteins, peptides, large molecules and/or small molecules which bind or connect to complimentary receiving or binding molecules.
In some embodiments complimentary molecules will be attached to the exterior surface of two groups of discrete carbon nanotubes such that when the two groups of discrete complimentary nanotubes are dispersed within the same solution, a 3D scaffold of carbon nanotubes may form or, in some cases, self-assemble as the attached complimentary molecules bind to each other. Tailoring of the complimentary molecules attached to the carbon nanotubes may be used to adjust the physical, chemical, and/or electrical properties of the resulting carbon nanotube network.
In addition to the described complementary molecules described above, catalysts, drugs, peptides, medicines, magnetic particles, or other desired large and/or small molecules may be attached to the exterior surface of the carbon nanotubes forming the described scaffold network. This may allow for the concentration, localization, and/or targeted delivery of the desired molecule to a specific location within a matrix or within a patient.
In some embodiments, the compositions disclosed herein can be used as a component in, or as, payload molecule delivery or drug delivery or controlled release formulations. In particular various drugs, including small molecule therapeutics, peptides, nucleic acids, or combinations thereof may be loaded onto nanotubes and delivered to specific locations. Discrete carbon nanotubes may be used to help small molecules/peptides/nucleic acids that are cell membrane impermeable or otherwise have difficulty crossing the cell membrane to pass through the cell membrane into the interior of a cell. Once the small molecule/peptide/nucleic acid has crossed the cell membrane, it may become significantly more effective. Small molecules are defined herein as having a molecular weight of about 500 Daltons or less.
The pro-apoptotic peptide KLAKLAK is known to be cell membrane impermeable. By loading the peptide onto discrete carbon nanotubes KLAKLAK is able to cross the cell membrane of LNCaP human prostate cancer cells and trigger apoptosis. The KLAKLAK-discrete carbon nanotube construct can lead to the apoptosis of up to 100% of targeted LNCaP human prostate cancer cells. Discrete carbon nanotubes may also be useful for delivering other small molecules/peptides/nucleic acids across the cell membranes of a wide variety of other cell types. Discrete carbon nanotubes may be arranged to have a high loading efficiency, thereby enabling the delivery of higher quantities of drugs or peptides. In some instances, this transport across the cell membrane may be accomplished without the need for targeting or permeation moieties to aid or enable the transport. In other instances, the discrete carbon nanotubes may be conjugated with a targeting moiety (ex. peptide, chemical ligand, antibody) in order to assist with the direction of a drug or small molecule/peptide/nucleic acid towards a specific target. Discrete carbon nanotubes alone are well tolerated and do not independently trigger apoptosis.
Peptides, small molecules, and nucleic acids and other drugs may be attached to the exterior of the discrete carbon nanotubes via Van der Waals, ionic, or covalent bonding. As discussed, the level of oxidation may be controlled in order to promote a specific interaction for a given drug or small molecule/peptide/nucleic acid. In some instances, drugs or peptides that are sufficiently small may localize to the interior of discrete carbon nanotubes. The process for filling the interior or discrete carbon nanotubes may take place at many temperatures, including at or below room temperature. In some instances, the discrete carbon nanotubes may be filled to capacity in as little as 60 minutes with both small and large molecule drugs.
The payload molecule can be selected from the group consisting of a drug molecule, a radiotracer molecule, a radiotherapy molecule, diagnostic imaging molecule, fluorescent tracer molecule, a protein molecule, and combinations thereof.
Exemplary types of payload molecules that may be covalently or non-covalently associated with the discrete functionalized carbon nanotubes disclosed herein may include, but are not limited to, proton pump inhibitors, H2-receptor antagonists, cytoprotectants, prostaglandin analogues, beta blockers, calcium channel blockers, diuretics, cardiac glycosides, antiarrhythmics, antianginal s, vasoconstrictors, vasodilators, ACE inhibitors, angiotensin receptor blockers, alpha blockers, anticoagulants, antiplatelet drugs, fibrinolytics, hypolipidemic agents, statins, hypnotics, antipsychotics, antidepressants, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, antiemetics, anticonvulsants, anxiolytic, barbiturates, stimulants, amphetamines, benzodiazepines, dopamine antagonists, antihistamines, cholinergics, anticholinergics, emetics, cannabinoids, 5-HT antagonists, NSAIDs, opioids, bronchodilator, antiallergics, mucolytics, corticosteroids, beta-receptor antagonists, anticholinergics, steroids, androgens, antiandrogens, growth hormones, thyroid hormones, anti-thyroid drugs, vasopressin analogues, antibiotics, antifungals, antituberculous drugs, antimalarials, antiviral drugs, antiprotozoal drugs, radioprotectants, chemotherapy drugs, cytostatic drugs, and cytotoxic drugs such as paclitaxel.
Magnetic particles may be bound or attached to the carbon nanotubes disclosed herein. The bound magnetic particles may be used to influence the orientation, location, or position of the carbon nanotube to which the magnetic particle is attached. Applying a magnetic field to carbon nanotubes bound to magnetic particles may allow the carbon nanotube to be moved to a particular location. Magnetic fields may be generated by natural magnets or electro-magnetic devices including at least, MRI, fMRI, or pulsed electromagnetic field generator devices. Additionally, a single magnetic field generation device may be utilized or multiple magnetic field generation devices may be used. In some embodiments, an array of EMF generators may be used to move CNTs bound to magnetic particles and/or cause such CNTs to vibrate, rotate, oscillate, or to direct CNTs from one specific position to another.
More than one species of magnetic particle may be bound to a single carbon nanotube. In some embodiments, the distinct species of magnetic particle may behave differently in the same magnetic field, thus creating an increased variety of possibilities for impacting the behavior of carbon nanotubes attached to more than one species of magnetic particle.
Magnetic particles bound to carbon nanotubes may comprise approximately 0.001 weight percent relative to carbon nanotube weight, or may comprise approximately 0.01 weight percent relative to carbon nanotube weight, or may comprise approximately 0.1 weight percent relative to carbon nanotube weight, or may comprise approximately 1 weight percent relative to carbon nanotube weight, or may comprise approximately 10. weight percent relative to carbon nanotube weight.
Carbon nanotubes bound to magnetic particles may additionally contain a payload molecule as discussed above or have peptides, small molecules, nucleic acids, or other drugs or molecules attached to their exterior. These combinations may allow the nanotube, along with its associated payload or substantially non-magnetic attached molecule to be directed to a particular location where the payload molecule of the attached molecule may be desired. In this manner, targeted molecules could be delivered to a particular location using a controlled magnetic field.
In some embodiments, magnetic fields may be used in order to flex or distort discrete carbon nanotubes or a network, matrix, or scaffold of discrete carbon nanotubes. If an open ended, payload carrying nanotube is flexed or distorted as described, this may increase the rate at which the interior payload molecule is emptied into the surrounding environment thereby enabling the controlled, targeted, and/or timed release of payload molecules. Similarly, the described flexing of a network of carbon nanotubes may increase the rate at which payload molecules are loaded into the interior of open ended nanotubes or allow molecules to be entrapped within the interior spaces of the nanotube network itself while remaining external to any particular nanotube.
Batteries comprising the compositions disclosed herein are also useful. Such batteries include lithium, nickel cadmium, or lead acid types.
Formulations comprising the compositions disclosed herein can further comprise an epoxy, a polyurethane, or an elastomer. Such formulations can be in the form of a dispersion. The formulations can also include nanoplate structures.
The compositions can further comprise at least one hydrophobic material in contact with at least one interior surface.
The present invention relates to a composition comprising a plurality of discrete carbon nanotubes and a plasticizer wherein the discrete carbon nanotubes have an aspect ratio of 10 to about 500, and wherein the carbon nanotubes are functionalized with oxygen species on their outermost wall surface. The discrete carbon nanotubes comprise an interior and exterior surface, each surface comprising an interior surface and exterior surface oxidized species content wherein the interior surface oxidized species content comprises from about 0.01 to less than about 1 percent relative to carbon nanotube weight and the exterior surface oxidized species content comprises more than about 1 to about 3 percent relative to carbon nanotube weight. The oxygen species can comprise carboxylic acids, phenols, or combinations thereof.
The composition can further comprise a plasticizer selected from the group consisting of dicarboxylic/tricarboxylic esters, timellitates, adipates, sebacates, maleates, glycols and polyethers, polymeric plasticizers, bio-based plasticizers and mixtures thereof. The composition can comprise plasticizers comprising a process oil selected from the group consisting of naphthenic oils, paraffin oils, paraben oils, aromatic oils, vegetable oils, seed oils, and mixtures thereof.
The composition can further comprise a plasticizer selected from the group of water immiscible solvents consisting of but not limited to zylene, pentane, methylethyle ketone, hexane, heptane, ethyl acetate, ethers, dichloromethane, dichloroethane, cyclohexane, chloroform, carbon tetrachloride, butyl acetate butanol, benzene or mixtures thereof.
In yet another embodiment the composition is further comprises an inorganic filler selected from the group consisting of silica, nano-clays, carbon black, graphene, glass fibers, and mixtures thereof.
In another embodiment the composition is in the form of free flowing particles.
In another embodiment, the composition comprises a plurality of discrete carbon nanotubes and a plasticizer wherein the discrete carbon nanotubes comprise from about 10 weight percent to about 90 weight percent, preferably 10 weight percent to 40 weight percent, most preferably 10 to 20 weight percent.
An another embodiment is a process to form a composition comprising discrete carbon nanotubes in a plasticizer comprising the steps of: a) selecting a plurality of discrete carbon nanotubes having an average aspect ratio of from about 10 to about 500, and an oxidative species content total level from about 1 to about 15% by weight, b) suspending the discrete carbon nanotubes in an aqueous medium (water) at a nanotube concentration from about 1% to about 10% by weight to form an aqueous medium/nanotube slurry, c) mixing the carbon nanotube/aqueous medium (e.g., water) slurry with at least one plasticizer at a temperature from about 30° C. to about 100° C. for sufficient time that the carbon nanotubes migrate from the water to the plasticizer to form a wet nanotube/plasticizer mixture, e) separating the water from the wet carbon nanotube/plasticizer mixture to form a dry nanotube/plasticizer mixture, and f) removing residual water from the dry nanotube/plasticizer mixture by drying from about 40° C. to about 120° C. to form an anhydrous nanotube/plasticizer mixture.
Another embodiment is the composition of discrete carbon nanotubes in a plasticizer further mixed with a least one rubber. The rubber can be natural or synthetic rubbers and is preferably selected from the from the group consisting of natural rubbers, polyisobutylene, polybutadiene and styrene-butadiene rubber, butyl rubber, polyisoprene, styrene-isoprene rubbers, styrene-isoprene rubbers, ethylene, propylene diene rubbers, silicones, polyurethanes, polyester-polyethers, hydrogenated and non-hydrogenated nitrile rubbers, halogen modified elastomers, flouro-elastomers, and combinations thereof.
Another embodiment is the composition of discrete carbon nanotubes in a plasticizer further mixed with at least one thermoplastic polymer or at least one thermoplastic elastomer. The thermoplastic can be selected from but is not limited to acrylics, polyamides, polyethylenes, polystyrenes, polycarbonates, methacrylics, phenols, polypropylene, polyolefins, such as polyolefin plastomers and elastomers, EPDM, and copolymers of ethylene, propylene and functional monomers.
Yet another embodiment is the composition of discrete carbon nanotubes in a plasticizer further mixed with at least one thermoset polymer, preferably an epoxy, or a polyurethane. The thermoset polymers can be selected from but is not limited to epoxy, polyurethane, or unsaturated polyester resins.
For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions describing specific embodiments of the disclosure.